Battery separator comprising hydrofluoric acid reduction material

Abstract

A separator including a polyolefin-based separator substrate having a porous structure, a first coating portion including a mixture of inorganic particles and a binder polymer, and a second coating portion including a material that reduces generation of hydrofluoric acid, wherein the first coating portion and the second coating portion are located on the separator substrate, are located in pores in the separator substrate, or are located on the separator substrate and in pores in the separator substrate.

The invention claimed is: 
     
       1. A separator comprising:
 a polyolefin-based separator substrate having a porous structure; 
 a first coating portion comprising a mixture of inorganic particles and a binder polymer; and 
 a second coating portion comprising a material that reduces generation of hydrofluoric acid, wherein 
 the first coating portion and the second coating portion are located on the separator substrate, are located in pores in the separator substrate, or are located on the separator substrate and in pores in the separator substrate. 
 
     
     
       2. The separator according to  claim 1 , wherein
 the first coating portion is located on the separator substrate, and 
 the second coating portion is located on the first coating portion. 
 
     
     
       3. The separator according to  claim 1 , wherein a mixed layer, comprising the first coating portion and the second coating portion in a mixed state, is located on the separator substrate. 
     
     
       4. The separator according to  claim 3 , wherein the second coating portion is present in an amount of 5 to 95 weight % based on a total weight of the mixed layer. 
     
     
       5. The separator according to  claim 3 , wherein the mixed layer is located in at least a portion of the pores in the separator substrate in addition to being located on the separator substrate. 
     
     
       6. The separator according to  claim 1 , wherein the material that reduces generation of hydrofluoric acid is present in an amount of 70 to 100 weight % based on a total amount of a solid content of the second coating portion. 
     
     
       7. The separator according to  claim 1 , wherein the material that reduces generation of hydrofluoric acid is a material comprising SiO 2 . 
     
     
       8. The separator according to  claim 7 , wherein the material comprising SiO 2  glass comprising SiO 2 . 
     
     
       9. The separator according to  claim 1  wherein the inorganic particles are at least one selected from a group consisting of (a) inorganic particles having a dielectric constant of 5 or more, (b) inorganic particles having piezoelectricity, and (c) inorganic particles haying lithium ion transmission capability. 
     
     
       10. The separator according to  claim 9 , wherein
 the (a) inorganic particles having a dielectric constant of 5 or more, when present, are SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , or SiC, 
 the (b) inorganic particles having piezoelectricity, when present form a potential difference due to a positive charge and a negative charge generated between opposite surfaces of the particles when a predetermined level of pressure is applied thereto, and are at least one selected from a group consisting of BaTiO 3 , Pb(Zr,Ti)O 3  (PZT), lead lanthanum zirconate titanate (PLZT), Pb(Mg 1/3 Nb 2/3 )O 3 —PbTiO 3  (PMN-PT), hafnia (HfO 2 ), SrTiO 3 , SnO 2 , CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 , Al 2 O 3 , TiO 2 , SiC, and a mixture thereof, and 
 the (c) inorganic particles having lithium ion transmission capability, when present, contain lithium elements that move lithium ions, rather than store lithium, and are at least one selected from a group consisting of lithium phosphate (Li 3 PO 4 ), lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0<x<2, 0<y<3), lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0<x<2, 0<y<1, 0<z<3), (LiAlTiP) x O y -based glass (0<x<4, 0<y<13), lithium lanthanum titanate (Li x La y TiO 3 , 0<x<2, 0<y<3), lithium germanium thiophosphate (Li x Ge y P z S w , 0<x<4, 0<y<1, 0<z<1, 0<w<5), lithium nitride (Li x ,N y , 0<x<4, 0<y<2), SiS 2 -based glass (Li x ,Si y S z , 0<x<3, 0<y<2, 0<z<4), P 2 S 5 -based glass (Li x P y S z , 0<x<3, 0<y<3, 0<z<7), and a mixture thereof. 
 
     
     
       11. The separator according to  claim 1 , wherein the binder polymer is at least one selected from a group consisting of polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-co-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl cellulose, and polyvinyl alcohol. 
     
     
       12. The separator according to  claim 1 , wherein the polyolefin-based separator substrate comprises at least one selected from a group consisting of high-density polyethylene, low-density polyethylene, linear low-density polyethylene, ultrahigh-molecular-weight polyethylene, and polypropylene. 
     
     
       13. A secondary battery comprising the separator according  claim 1 . 
     
     
       14. The separator according to  claim 1 , wherein the material that reduces generation of hydrofluoric acid has a property of reacting with hydrofluoric acid to remove the hydrofluoric acid. 
     
     
       15. the separator according to  claim 14 , wherein the material that reduces generation of hydrofluoric acid is at least one selected from a group consisting of SiO 2 , Na 2 CO 3  and K 2 CO 3 . 
     
     
       16. The separator according to  claim 3 , wherein the second coating portion is present in an amount of 10 to 90 weight % based on a total weight of the mixed layer.